1. Field of the Invention
The present invention relates to an ink jet apparatus based on a temperature calculation and an ink jet head control method, and more particularly to an ink jet apparatus which uses an ink jet head of a type which utilizes thermal energy for discharging liquid and a control method of the ink jet head.
2. Related Background Art
An ink jet system which permits application of a small amount of liquid to a medium has been widely used in various fields such as printing, image recording and drying, and it is so rich in the application that the applications to other fields have been expected.
For example, as a personal computer, a word processor and a facsimile machine have become popular in offices and homes, printers of various recording systems have been developed as output devices for those equipments. Among others, the ink jet recording system is most appropriate for personal use in the office because of its low record noise and a high quality of record for various kinds of recording media as well as its compactness. Of the ink jet recording system, a bubble jet system which is a thermal system of high drive response has been one of main streams. In this system, an electrical signal is converted to a heat by a recording head to film-boil ink, which is in turn discharged to a recording medium by utilizing a pressure by boiling.
Ink droplets deposited to the recording medium spread on the recording medium to form dots. An image is formed and recorded by an aggregation of dots. An area of one dot largely depends on a size of ink droplet or an amount of discharged ink. Thus, in order to attain high quality recording in the ink jet recording system, it is most important to control the amount of discharge. When a drive pulse applied to a heat generating element is constant, the amount of discharge depends on a temperature of the ink in the vicinity of the heat generating element. Thus, it is necessary to control the ink temperature, but since it is practically difficult to control it, it is common to control a temperature of a chip which forms the recording head instead of controlling the ink temperature. Usually, a temperature sensor is provided in the recording head chip but it has been proposed to use a method for estimating the temperature of the recording head from a record pattern instead of or together with the provision of the temperature sensor while taking the increase in a cost of an amplifier and noise countermeasures as well as reliability of the temperature sensor into consideration.
However, as the drive frequency has increased and the number of discharge ports (or ejection outlets) per chip has increased by the recent speedup of the recording speed, a change of the recording chip temperature for time has increased and it has been strongly demanded to use more precise method than the prior art temperature estimation method. The high preciseness may be attained by shortening the time of temperature estimation calculation but in this method, a burden of the recording apparatus to the calculation increase as the time is shortened and a throughput is reduced, or it is required to enhance the performance of an MPU which is calculation means.